Throughout this specification the use of the word “inventor” in singular form may be taken as reference to one (singular) inventor or more than one (plural) inventor of the present invention.
It is to be appreciated that any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the present invention. Further, the discussion throughout this specification comes about due to the realisation of the inventor and/or the identification of certain related art problems by the inventor. Moreover, any discussion of material such as documents, devices, acts or knowledge in this specification is included to explain the context of the invention in terms of the inventor's knowledge and experience and, accordingly, any such discussion should not be taken as an admission that any of the material forms part of the prior art base or the common general knowledge in the relevant art in Australia, or elsewhere, on or before the priority date of the disclosure and claims herein.
In the application of RFID technology to Casinos, casino managers are interested in the capability of recording all of the bets being placed within their premises in real time. This requires a precise and reliable means for identifying the various gaming chips disposed inside, or in close proximity to, the betting zones, as delineated by the markings disposed on the surface of the gaming tables. Various systems have been developed which have the ability to automatically flag in real-time, or in near rear time, any unusual and suspicious events. These systems can also continuously tracking the performance of individual players and are used to assess the short, medium and long-term performance of casino personnel.
When the objects are gaming chips, tokens, or plaques, and the surface is a casino gaming table such as Baccarat, Mini-baccarat, Blackjack or Pai Gow Poker, the demarked areas of interest are called “betting spots” or areas associated with each player's bet. The table top is delineated with graphics and other indicia on a covering material called a “layout”. In play and placing bets, the chips may be stacked in columns up to 25 high, for example. For Blackjack, allowance must also be made for the placement of “double down” or “split” bets which are placed just outside the “betting spot”. For Baccarat the player betting areas are adjacent and also include adjacent “banker/player/tie” locations.
When automatically communicating with objects which have an embedded RFID chip, responses must be correctly associated with a player location/bet area for this information to be useful to a gaming table system tracking bets and payouts. An RFID inlay, i.e., the “tag,” is disposed within the gaming chip. The inlay is an electronics assembly substrate that connects a planar coupler coil or loop and the semiconductor RFID die. Accordingly, it is necessary to know, the precise location or presence of “tagged objects” within a demarked area. The size of the area may cover several centimeters of extent and adjacent areas may have contiguous narrow boundaries of the order of 6 mm. All sensing equipment is preferably below the table top and out of sight of the players. That is, it is not desired to place couplers, antennas, etc., above the table top.
In one approach, radio frequency identification (RFID) technology based on radiated fields (far fields) operating at approved frequencies such as 433 MHz, 915 MHz, 2.4 GHz etc has been used. While promising, this technology has a major drawback. It is not particularly precise in terms of spatial resolution. As a result, its potential is limited to its application to gaming surfaces with single betting areas, such as poker tables, or to tables with betting areas separated by relatively large spaces. Because of both its operating principle and the frequencies at which it operates, this technology is subject to effects that disturb the local field. For example antennas may be detuned by parasitic capacitance (people and metal objects). Signals may be attenuated by the human body. Further, signal propagation may be affected by multi-path phenomena. Accordingly, existing RFID based technology is considered inadequate when applied to gaming surfaces having multiple betting areas in close proximity to each other, such as the ones used in blackjack or baccarat. The problem is exacerbated when the gaming chips are disposed on the separation lines between betting areas, such as roulette tables.
Other prior art attempts at addressing these problems have used inductively coupled RFID in the HF frequency band. The terms “Induction field” or “induction coupler” refer to the domain of interacting short range magnetic fields (H fields) that operate by “transformer action” rather than electromagnetic radiation. Magnetic coupling RFID based technology typically operates at approved frequencies in the 125 KHz or 13.56 MHz bands. Because of the inherent “near field” characteristics of this technology, the signal dies off very rapidly beyond the intended coverage, area and surrounding environment variations have much less of an impact. Those of ordinary skill in the art will understand that the term “read,” or “reading chips,” refers to an RFID Reader electronics unit transmitting one or more interrogation messages to the RFID transponder disposed within the gaming chip. The interrogation message supplies a wireless “induction field” that provides power to the passive RFID inlay. The class of RFID used is “passive” where transponders are powered solely by capturing energy from the Reader-generated impinging field. The RFID inlay receives the interrogation message(s) and provides a response to the reader. These RFID devices generally also follow the rule of Reader Talks First (RTF).
However, there are drawbacks associated with this approach as well. While the transformer based induction coupler technology represents an improvement over the radiated far-field RFID technology, it is not accurate enough to discriminate between closely spaced betting zones. As noted above, chips may be stacked on top of each other. Any approved system must provide communication with a chip on the top of a stack that may be 25 chips high (for example). The lateral fall-off characteristics of the coupler-generated H field (magnetic field) which can be computed by using the Biot-Savart law. Those of ordinary skill in the art will understand that the magnetic field produced by an embedded loop is roughly spherically shaped. Accordingly, the magnetic field extends approximately the same distance laterally as it does vertically. In particular, the field strength required to reach the top of the chip stack will also result in the field impinging on the neighbouring betting spot. This phenomenon is commonly referred to as “cross read” or “cross talk.”
U.S. Pat. No. 7,612,675 describes one attempt to address these various problems. In essence, U.S. Pat. No. 7,612,675 provides a ‘jamming’ antenna, which in effect ‘jams’ the cross talk signal. Unfortunately, the reader associated with the ‘jamming’ antenna is complex. The system disclosed requires a reader, a jammer and a flux canceller.